模拟降雨下前期含水量对黄绵土坡面产流产沙过程的影响

Effect of Antecedent Soil Moisture on Runoff and Sediment Yield on Loess Slope Under Simulated Rainfall

为探究不同前期土壤含水量条件下坡面产流产沙特征及产流产沙关系,以安塞黄绵土为研究对象,通过设置6个前期土壤含水量处理(5%,10%,15%,20%,25%,30%),采用室内人工模拟降雨试验来系统研究前期土壤含水量对坡面产流产沙过程的影响。每个含水量处理设置2个重复,坡面坡度为15°,设计雨强为90 mm/h,降雨历时为1 h。结果表明:(1)随着前期土壤含水量的升高,坡面初始产流时间幂函数减小,产流量线性增大。(2)坡面土壤流失量随前期土壤含水量增大呈幂函数增加,高含水量组(29.3%)土壤流失量分别是低含水量组(5.8%和10.6%)和中含水量组(15.3%,20.4%,25.1%)的86.1,8.9倍。当前期含水量接近饱和时,坡面侵蚀加剧,土壤流失量迅速增加。(3)不同前期土壤含水量条件下坡面产流量与产沙量呈幂函数关系,当产流速率超过1.4 L/min,产沙量迅速增加甚至翻倍,呈“水大沙多”的特点。前期土壤含水量通过影响入渗产流和改变径流泥沙关系双重作用来影响坡面产沙。因此,对黄绵土坡面而言,应注意防范连绵持久降雨后暴雨或特大暴雨所造成的水土流失问题,可采取耕作、植被覆盖等措施维持适当土壤含水量使土层不饱和来减少侵蚀。研究结果为黄土高原水土资源保护和管理提供科学依据。

In order to explore the characteristics of runoff and sediment yield and the relationship between runoff and sediment yield on the slope under different antecedent soil moisture conditions,this paper took Ansai loessial soil as the research object,and systematically studied the influence of antecedent soil moisture on runoff and sediment on slope by setting six antecedent soil moisture treatments(5%,10%,15%,20%,25%,30%).Two repetitions were set for each water content treatment,the slope gradient was 15°,the rainfall intensity were set to 90 mm/h,and the rainfall duration was set to 1 hour.The results showed that:(1)With the increase of antecedent soil moisture,the initial runoff time decreased as a power function,and the runoff increased linearly.(2)The amount of soil loss on the slope increased as a power function with the increase of antecedent soil moisture.The amount of soil loss in the high antecedent soil moisture group(29.3%)was 86.1 and 8.9 times that in the low water content group(5.8%and 10.6%)and the medium water content group(15.3%,20.4%and 25.1%).When antecedent soil moisture was close to saturation,the slope erosion intensified and the amount of soil loss increased rapidly.(3)Under the conditions of different antecedent soil moisture,the relationship between slope runoff and sediment yield was a power function.When the runoff yield rate exceeded 1.4 L/min,the sediment yield increased rapidly or even doubled,showing the characteristics of“large water and more sediment”.Antecedent soil moisture affected slope sediment yield by affecting infiltration runoff and changing the relationship between runoff and sediment.Therefore,for the loess slope,attention should be paid to preventing soil erosion caused by rainstorm or extreme rainstorm after continuous and lasting rainfall.Measures such as cultivation and vegetation cover can be taken to maintain appropriate soil water content and make the soil layer unsaturated to reduce erosion.The results provide a scientific basis for the protection and management of soil and water resources in the Loess Plateau.